Recurrent Early Pregnancy Loss - 4 - Anatomic Causes
Wednesday, March 28, 2007
Kenneth F. Trofatter, Jr., MD, PhD
Early in the embryonic development of the female genital tract, the uterus begins as separate structures on both side of the pelvis. In normal circumstances, as development progresses, these separate structures move to the midline and fuse, forming a single uterus, cervix and vagina. In 1 out of every 200 to 600 women, this process is interrupted during some point in the developmental process. The congenital malformations that result from this are called ‘Mullerian duct abnormalities.’ These abnormalities can range from complete lack of fusion of the Mullerian duct, resulting in two completely separate uteruses (uterus didelphys) with cervixes (and sometimes two vaginas); a partial lack of fusion, resulting in a uterus with two cavities and a single cervix (bicornuate uterus); or a uterus that has a single cavity that is divided in the midline to varying degrees by a fibromuscular wedge of tissue (septate uterus).
Under some circumstances, only one of the embryological precursors for the genital tract will develop forming a single (usually smaller) uterus (unicornate uterus) and cervix which deviates to the side of its origin. The latter are frequently associated with urinary tract abnormalities, such as an absent kidney, usually on the side which did not have normal development of the Mullerian duct. Mullerian abnormalities result in smaller uterine cavities, fewer suitable implantation sites, and aberrations of vascularization (blood supply) that may contribute to both early and later pregnancy losses. Indeed, these abnormalities are frequently also accompanied by cervical incompetence which has been addressed in other posts. One other condition associated with a small, abnormally-shaped uterine cavity and high rate of unexplained first trimester losses is seen in women who were exposed to DES (diethyl stilbesterol) in utero. Fortunately, since the last DES used in reproductive age women was given in the early 1970’s, this is quickly becoming less of a problem.
The most common neoplasms (‘tumors’) of the uterus are fibroids (leiomyomata). These are characterized by an excessive proliferation of the smooth muscle cells and connective tissues that are normally present in the muscular wall of the uterus. The cause of fibroids is unknown. They are generally ‘benign’ (not cancer) and can be located just beneath the intraabdominal surface of the uterus (subserosal fibroids), within the muscular wall (intramural fibroids), or beneath the inner lining (endometrium) of the ueterus (submucosal). At times they can project either into the abdomen or into the uterine cavity on ‘stalks’ and these are referred to as ‘pedunculated fibroids.’ Uterine fibroids can distort and/or decrease the volume of the uterine cavity, compromise implantation or growth of the placenta by stretching and thinning the endometrium or by stealing blood supply, and if located in proximity to the cervix, may distort the internal cervical opening (os) sufficiently to cause cervical incompetence as well.
Endometrial polyps result from localized overgrowth (proliferation) of the endometrium and also produce a stalked projection into the uterine cavity. Both endometrial polyps and intrauterine fibroids (pedunculated or not), in addition to causing distortion of the uterine cavity, are often sites of chronic inflammation and/or infection and this may be the means by which they contribute to early pregnancy losses. Under these circumstances they may function as a ‘natural’ analog to an intrauterine device (IUD), by preventing proper implantation or disturbing the delicate immunologic balance of early pregnancy, interrupting the growth of the developing embryo.
During our surgical care for patients, we may also induce damage to the endometrium that can lead to recurrent pregnancy loss. These are classified under the ‘iatrogenic’ causes for recurrent pregnancy loss. For example, many patients who have early pregnancy losses (or who have undergone elective termination of pregnancy in the past) will undergo dilatation and curettage (D&C) procedures to complete the evacuation of the pregnancy tissues from the uterus. If a D&C is performed too aggressively, or if an intrauterine infection is present as either the cause or the result of a pregnancy loss at the time a D&C is performed, the result can be scarring of the endometrial cavity, termed Asherman’s syndrome. At times this scarring can be so extensive (especially if infection was present at the time of the procedure), the woman will stop having periods altogether. Damage to the endometrial cavity can also result during the surgical removal of endometrial polyps or intrauterine fibroids, even when these procedures are performed through an operating scope (hysteroscopy). Again, regardless of the cause, when such damage or scarring is present, the common threads of poor implantation sites, decreased blood supply, and inflammation can raise their ugly heads to interrupt early pregnancies on a repetitive basis...
9 Comments:
At Sun Apr 13, 04:21:00 PM 2008,
Julia Mangan said…
I had to have 2 D&C's within 3 weeks of each other (the 2nd ended up being for a retained placenta whereas the 1st was the result of a miscarriage) in 2006. I now suspect Asherman's as I have not been able to conceive in 5 months time in spite of the fact I ovulate regularly and have timed intercourse favorably each month. (I chart my cycles using the fertility awareness method and have for years prior to trying to conceive as well.) I have read, if I do indeed have Asherman's, I should not be trying to conceive so I have set-up an appointment with my gynecologist to have this checked. My question to you is, is the average gynecologist aware of this condition and able to diagnose it? Or should I be seeing a specialist?
At Tue Apr 15, 07:42:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
Hi Julia: It depends on the experience of the gynecologist. I usually send patients with suspected Asherman's to a specialist in Reproductive Endocrinology and Infertility, so you might ask your doctor about that as well. If you are still having periods, then you may just have a few adhesions, but then again, you may have also developed another reason for your 'infertility' that is unrelated to the D&Cs! Best of luck and let us know what you find out. Dr T
At Tue Apr 15, 07:46:00 PM 2008,
Julia Mangan said…
Thank you for the response. I have an appt. scheduled to at least rule this out. Hopefully, I do not have this condition but want to at least rule it out.
At Fri Jul 11, 03:08:00 PM 2008,
asher said…
Dr. T,
I am 39 years-old and have been diagnosed with Asherman's. After my C-section in 2005, I had to have a D&C 5 months later to remove some placenta that was left near the cervix. I never did get a full menses back after that. I ovulate regularly and have one spot for a menses. I was referred to a Reproductive Specialist and discovered that I now have scarring at the point of the D&C scraping to where an HSG cannot even get into the uterine cavity. I have had one hysteroscopy (March 2008) that opened the cervix canal a little higher, but still an HSG cannot get into the uterus. Yesterday, a intervaginal ultrasound demonstrated that there is some uterine lining in spots, but not a continuous lining. Before the first hysteroscopy, there was only one spot of lining on the right side. My doctor says that we may have about a 1 in 4 chance of opening the uterus with another hysteroscopy. With my FSH levels at 13, he believes that I probably have a very slim chance if any of getting pregnant again if I have a successful hysteroscopy. However, I am more concerned about opening the uterus to have a normal menstrual cycle thinking that this is beneficial to allow the flow to come out versus "being stuck" behing the blocked cervix. The other option the doctor gave me is hysterectomy. I don't know if I am ready to go down that path without getting more opinions. Pregnancy is a bonus if it happens. Can you explain to me what the risks may be to live with the blocked cervix and not do anything. Would you advise your patients to try the hysteroscopy again? Is it a risk to have intercourse around ovulation with Asherman's?
At Mon Jul 14, 07:15:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To asher: Even with only a very small openong, menstrual flow can usually escape the uterus. From what you describe, your bleeding is light probably because of the absence of healthy endometrium rather than as a result of the scar tissue at the cervical opening. If the cervix is completely blocked, you could possibly accumulate blood and tissue inside the uterus over time and that could eventually result in a pelvic infection. The only risk of intercourse that I can imagine is that you could get pregnant and have an abnormal implantation or an ectopic pregnancy because of the scar tissue. Best of luck to you. Dr T
At Thu Sep 04, 02:16:00 PM 2008,
Anonymous said…
I just had an ultrasound at 12 weeks and found out that I have a 5mm fibroid on the lower part of my uterus. The fibroid is within the wall of the uterus. From what I understand, this will increase my chances of needing a c-section due to the location. Would the fibroid cause any other risks to my pregnancy? Why is it that the OB did not know about the fibroid before now? Thanks Dr. T.
At Sun Sep 21, 04:58:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To anonymopus Sept 4: I apologize for the delay in answering, but I JUST got your comment delivered to my mailbox today. The fibroid probably measured 5 cm (50 mm) or about 2 inches. I would not panic over that at 12 weeks. In fact some findings that are thought to be fibroids that early are simply localized contarctions in the uterus. Supposing the diagnosis is accurate, if the fibroid grew significantly, and was located low enough in the uterus, it could obstruct descent of the fetal head into the pelvis, thereby increasing your risk for a c/section. If the fibroid outgrows its blood supply and 'degenerates' (as they can do under the influence of pregnancy hormones), it could cause pain or even premature labor and delivery. If it is close to the cervical opening, it could distort the interal cervical os and lead to cervical insufficiency (incompetent cervix). Anyway, usually they do not cause any of those problems, so let us know how things turn out and best wishes! Dr T
At Tue Oct 21, 12:07:00 PM 2008,
majda said…
Dr. Trofatter;
I am 7 weeks pregnant and i have my first appointment next week. 2 years ago, my gyno told me that my uterus is moved to the right due to possible infection earlier in life and that right ovary is very close to the uterus. Will I have a high risk pregnancy? Or should the uterus move back to the center on it's own? Thank you
At Wed Oct 29, 07:02:00 PM 2008,
Kenneth F. Trofatter, Jr., MD, PhD said…
To majda: the uterus will take all the space it needs! That alone should not make this a 'high risk' pregnancy. Best wishes.
Dr T
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